1. Field of the Invention
The present invention relates to a mounting apparatus and mounting method of mounting a flexible board onto a display board. Specifically, the mounting refers to electrically connecting terminal electrode rows. For example, the present invention relates to a mounting apparatus and mounting method of connecting a terminal electrode of a TFT (Thin Film Transistor) liquid crystal display and a terminal electrode of a TCP (Tape Carrier Package) of a flexible printed circuit board mounted with an LSI (Large Scale Integrated circuit) for driving.
2. Description of the Background Art
Referring to FIGS. 10 and 11, a conventional method of connecting a liquid crystal display 2 containing a liquid crystal layer 1 and a flexible printed circuit board 4 mounted with an LSI for driving will be described. In connecting, as shown in FIG. 10, a terminal electrode 3 of liquid crystal display 2 and a terminal electrode 5 of flexible printed circuit board 4 are bonded together, for example by thermocompression through an adhesive agent 6. For thermocompression, a cylinder-driven heater tool 8 is lowered and pressed.
FIG. 11 shows the structure of FIG. 10 viewed from above, where the terminal electrodes are bonded by thermocompression. It is generally known that flexible printed circuit board 4 stretches during thermocompression. It appears in FIG. 11 that terminal electrodes 3 and 5 are perfectly in alignment. However, it can be seen in FIG. 12, showing in enlargement outermost terminal electrodes 3 and 5, that terminal electrode 5 is displaced by a displacement amount 7 in the electrode width direction according to a stretch amount of flexible printed circuit board 4.
A common practice to adjust the stretch amount of flexible printed circuit board 4 is that an operator measures displacement amount 7 with use of a microscope or the like, and repeats thermocompression with different parameters of compressing temperature, pressure, time and so on to determine displacement amount 7. Thus, the operator must go through a continuing process of trial and error to find appropriate conditions for thermocompression.
Particularly, conventional terminal electrodes have a large pitch to allow for stretching of the flexible printed circuit board. In addition, a specific method of controlling the stretch amount of flexible printed circuit board has been unknown. For these reasons, in the conventional apparatuses, variation in stretch amount according to a material or size is restrained based on personal judgement and experience of an operator, for example, by varying an air flow as a variable parameter to adjust the lowering speed of a heater tool.
In recent years, flexible printed circuit boards are becoming more sophisticated and the pitch of terminal electrodes is reduced accordingly. This leads to the need for properly estimating the stretch amount of flexible printed circuit boards. Thus, the conventional mounting method is no longer satisfactory.
The above described conventional mounting technique suffers from three major problems.
First, the adjustment of the compressing temperature, pressure and time by cylinder-driven heater tool 8 is based on personal judgement and experience of the operator, whereby the stretch amount of flexible printed circuit board 4 is not quantitatively adjusted in the optimum manner with respect to the required adjustment amount. Depending on the skill level of the operator, such adjustment usually involves a considerable amount of time. Thus, the method is not satisfactory if the adjustment must be made in a short period of time.
Secondly, cylinder-driven heater tool 8 involves a long stroke. Thus, pressure variation in the cylinder is large and a load applied to an object fluctuates. Note that the compression pressure is obtained by dividing the load by an area subjected to compression. This causes variation is stretch amount and displacement inconsistency of terminal electrodes 3 and 5. As such, the conventional technique cannot fully cope with reduced pitches of terminal electrode rows to be connected.
Thirdly, the measurement of displacement amount 7 must be made by the operator with use of a microscope since an image processing apparatuses is unable to detect displacement amount 7 between terminal electrodes 3 and 5. The measurement involves a considerable amount of time. In addition, terminal electrode 5 of the flexible printed circuit board is usually formed by etching with a liquid agent and hence formed to have a section in a trapezoid shape as shown in FIG. 13. As a result, a measurement error of several xcexcm is caused, for example depending on which of positions A, B and C the operator regards as the end of terminal electrode 5. Further, there is a variation in measurement result of displacement amount 7 due to a difference in stretch amount of terminal electrode 5 between compressed and non-compressed portions. Moreover, such manual measurement by the microscope does not immediately provide a distance between central lines of terminal electrodes 5 at both ends of the terminal electrode rows of flexible printed circuit board 4, i.e., a total pitch. Thus, feedback as well as real time elimination of variation in stretch amount are impossible.
In view of the above, the present invention aims at providing a mounting apparatus and mounting method which enables detection and adjustment of a stretch amount of a flexible printed circuit board in a short period of time, and which is capable of avoiding displacement inconsistency.
To achieve the above mentioned object, a mounting apparatus according to one aspect of the present invention includes: a heater head for bonding by thermocompression a display board and a flexible print circuit board in such a way that a first terminal electrode row of the display board and a second terminal electrode row of the flexible printed circuit board are electrically connected; a heater head driving portion for driving the heater head in such a way that the heater head compresses the display board and flexible printed circuit board by a prescribed load; and a stretch amount controlling portion for adjusting a load change per unit of time after the heater head starts compressing the flexible printed circuit board by the heater head driving portion as well as the time at which a required load is attained to control the stretch amount of the second terminal electrode row caused by thermocompression.
With the above described structure, the stretch amount of the flexible printed circuit board can be controlled by adjusting the load change and the time at which the required load is attained. Thus, variation in stretch amount which has conventionally been measured based on personal judgement and experience of an operator can be eliminated. Thus, displacement inconsistency can be avoided.
A mounting apparatus according to another aspect of the present invention includes: a heater head for bonding by thermocompression a display board and a flexible printed circuit board in such a way that a first terminal electrode row of the display board and a second terminal electrode row of the flexible printed circuit board are electrically connected; a heater head driving portion for driving the heater head in such a way that the heater head compresses the display board and the flexible printed circuit board by a prescribed load; and a stretch amount controlling portion for adjusting a speed at which the heater head driving portion drives the heater head toward the flexible printed circuit board to control the stretch amount of the second terminal electrode row caused by thermocompression.
With the above described structure, the speed at which the heater head is moved toward the flexible printed circuit board is adjusted and variation in speed among compression cycles is controlled, whereby the stretch amount of the flexible printed circuit board can be controlled. As a result, displacement inconsistency can be avoided.
Preferably, the above described invention includes: a displacement amount detecting portion for detecting a displacement amount of positioning patterns formed on either side of the second terminal electrode row with respect to reference patterns formed on either side of the first terminal electrode row; a stretch amount calculating portion for calculating the stretch amount of the second terminal electrode row based on the displacement amount; and a correction amount calculating portion for calculating a correction amount corresponding to a difference between the stretch amounts of the first and second terminal electrode rows based on the stretch amount of the second terminal electrode row.
With the above described structure, the correction amount can be calculated by the correction amount calculating portion, whereby the correction amount can be accurately found in a short period of time unlike the conventional case of personal judgement and experience of the operator.
In the above described invention, preferably, the stretch amount controlling portion controls by feeding back the correction amount. With this structure, the problem associated with variation in stretch amount is accurately alleviated in real time since correction is made based on actual data, rather than on personal judgement and experience of the operator as in the conventional case.
Preferably, the above described invention includes a data holding portion for holding data regarding a relationship between an operation parameter and a stretch amount of the second terminal electrode row. The stretch amount controlling portion determines a necessary control method from data held in the data holding portion for control. With this structure, a necessary control method is rapidly determined for control. In addition, a variety of data provides better control.
In a mounting method according to one aspect of the present invention, a display board and a flexible printed circuit board are bonded by thermocompression with use of a heater head in such a way that a first terminal electrode row of the display board and a second terminal electrode row of the flexible printed circuit board are electrically connected, where a load change per unit of time after the heater head starts compressing against the flexible printed circuit board as well as the time at which a required load is attained are controlled, so that a stretch amount of the second terminal electrode row caused by thermocompression is controlled.
With the above described method, the load change and the time at which the required load is attained are adjusted to control the stretch amount of the flexible printed circuit board. Thus, variation in stretch amount which is conventionally measured based on personal judgement and experience of the operator can be eliminated. Thus, displacement inconsistency can be avoided.
In a mounting method according to another aspect of the present invention, a display board and a flexible printed circuit board are bonded by thermocompression with use of a heater head in such a way that a first terminal electrode row of the display board and second terminal electrode row of the flexible printed circuit board are electrically connected. A speed at which the heater head is moved toward the flexible printed circuit board is controlled, so that the stretch amount of the second terminal electrode row caused by thermocompression is controlled.
With the above described structure, the speed at which the heater head is moved toward the flexible printed circuit board is adjusted and variation in speed during compression is controlled, so that the stretch amount of the flexible printed circuit board can be controlled. As a result, displacement inconsistency can be avoided.
In the above described invention, preferably, control of the load change and the time at which the required load is attained refers to substantially stabilizing the load change and the time at which the required load is attained. With this structure, the stretch amount can be stabilized with a relatively simple mechanism and displacement inconsistency can be alleviated.
In the above described invention, preferably, control of the load change and the time at which the required load is attained refers to quantitative control to set the stretch amount at a desired value. With this structure, the stretch amount can be maintained at the desired value by quantitative control. As a result, displacement inconsistency can be alleviated.
Preferably, the above described invention includes: a displacement amount detecting step of detecting a displacement amount of positioning patterns formed on either side of the second terminal electrode row with respect to reference patterns formed on either side of the first terminal electrode row; a stretch amount calculating step of calculating a stretch amount of the second terminal electrode row based on the displacement amount; and a correction amount calculating step of calculating a correction amount corresponding to a difference between stretch amounts of the first and second terminal electrode rows based on the stretch amount of the second terminal electrode row, where quantitative control is performed by feeding back the correction amount.
With the above described structure, the correction amount can be rapidly and objectively found unlike the conventional case where the correction amount is measured based on personal judgement and experience of the operator for feedback control. Thus, the requirements for real time adjustment of stretch amount on a production line can be satisfied with no problem.
Preferably, the above described invention includes: a preliminary bonding step of preliminary fixing a relative position of the flexible printed circuit board and the heater head; a displacement amount detecting step performed after the preliminary bonding step; and a regular bonding step performed after the displacement amount detecting step. With this method, stable measurement is enabled since the measurement is performed with the relative position fixed. The obtained measurement result is made available for regular bonding, so that more accurate bonding is enabled.
Preferably, the above described invention includes: a relative position determining step of determining a relative positional relationship between reference patterns formed on either side of the first terminal electrode row and a relative positional relationship between positional patterns formed on either side of the second terminal electrode row; a preliminary bonding step of preliminary fixing a relative position of the flexible printed circuit board and the heater head performed after the relative position determining step; a stretch amount calculating step of calculating a stretch amount of the second terminal electrode row based on information obtained by the relative position determining step; a correction amount calculating step of calculating a correction amount corresponding to a difference between stretch amounts of the first and second terminal electrode rows based on the stretch amount of the second terminal electrode row; and a regular bonding step performed after the preliminary bonding step. With this method, the stretch amount of the second terminal electrode row can be found even if a measurement operation cannot be performed between the preliminary bonding step and the regular bonding step, whereby proper control can be performed during the regular bonding.